Project Summary/Abstract The goal of this project is to develop bioactivated magnetic resonance(MR) contrast agents for the imaging of in vivo processes, ranging from gene expression to secondary messenger activation. This project is focused on obtaining insights into the interrelated problems of developmental biology and clinical diseases by i. generating MR probes that function as real-time in vivo enzyme reporters, ii. Track gene expression in whole animals and correlate this information with ongoing developmental events, and iii. develop biocompatible scaffolds for the efficient delivery of these agents in experimental animals and potentially humans. In order to maximize the impact of this technique, functional contrast agents must be investigated and developed. Further, the study of developmental biology in whole animals will result in a deeper understanding of the role of spatial organization with mechanism. Therefore, to create an in vivo assay of enzymatic activities and detection of secondary messengers, MR contrast agents will be designed and synthesized with removable protection groups that largely prevent the access of water to a paramagnetic center. By limiting the access of bulk water (q- modulation) the unprocessed agent is designed to be an ineffective contrast agent. We have defined 5 primary objectives: 1.Synthesize and characterize MRI contrast agents with enzyme substrates as blocking groups of water (q-modulation) 2. Use computational modeling to direct synthetic efforts towards new q-modulated agents. 3.Develop targeted contrast agents and methods of amplifying the contrast signal. 4. Investigate delivery and the uptake mechanisms by which the agents are internalized by cells. 5. Evaluate the effectiveness of the agents in preclinical rodent models and other in vivo systems. Several tetraazamacrocyclic architectures will be synthesized and investigated. We will focus on the schematically represented structures I- V where the arrows represent the site of enzymatic attack for the irreversibly activated agents (I-III).